<div></div>

div {
  width: 300px;
  border: 1px solid red;
}
div::before {
  content: url('data:image/svg+xml;utf8,<svg version="1.1" id="" xmlns="http://www.w3.org/2000/svg" width="100%" height="100%" xmlns:xlink="http://www.w3.org/1999/xlink"  style="" xml:space="preserve"><path d="M150 0 L75 200 L225 200 Z"></path></svg>');
  display: block;
  width: 300px;
}